This invention relates to new and useful improvements in tubing injectors, particularly tubing injectors adapted to be used with long coiled metal tubing for injection and retraction down a well bore.
Heretofore, tubing injectors suffer from two principal disadvantages. Firstly it is difficult to maintain and to adjust the pressure of the drive chains upon the tubing as it is inserted and withdrawn, it being understood that the necessary pressure changes not only with bore hole conditions but also with the length of tubing extending below the injector.
Secondly, conventional tubing injectors include dies attached to the drive chains which are of a single diameter so that they are only suited for use with one diameter of tubing. This means that if a different diameter of tubing is used, then the dies have to be changed.
Furthermore, couplings and other components are often present along the length of the drill tubing and it is difficult to accommodate these couplings and other components, as they pass through the injector because of the different diameters of these couplings and/or components.